Japanese patent application publication No. HEI11-68893 discloses a wireless telephone system configured of a base unit and handsets by which a user can remotely control household electric devices, such as lighting and an air conditioner. Specifically, the user uses the communication function of the wireless telephone system to transmit a signal for controlling household electric devices from the handset to the base unit. Upon receiving this signal, the base unit outputs an infrared signal to the household electric device, enabling the user to control the electric devices remotely. The base unit and handsets of the wireless telephone system communicate with each other using conventional radio frequency signals. The user can command the base unit from a handset in a remote location from the base unit to transmit an infrared signal to electric devices in the vicinity of the base unit. The base unit uses an indoor infrared signal commonly used in infrared remote controllers for household appliances. The user can also transmit control signals directly to electric devices in the vicinity of the handset using an infrared transmitter provided in the handset.
However, remote control systems popularly used with household appliances can only transmit infrared signals in one direction from the remote control to the appliance. Currently, infrared signals are not transmitted in the opposite direction, which could enable the user of the remote controller to learn the status of the household appliances. As a result, the wireless telephone system described above can only transmit infrared signals from the base unit or handset to the electric devices. Hence, when the user wishes to remotely control a household appliance using a handset from a separate room, the user cannot visually confirm the operating state of the household appliance and, therefore, has no means of confirming with the handset whether the appliance has performed the desired operation. If the lens of the infrared transmitter is dirty, for example, preventing the infrared signal from reaching the household appliance, or if the household appliance cannot receive the signal due to some issue on the appliance side, the electric appliance will not be controlled as desired. By not being able to determine the status of the household appliances, the user cannot fully enjoy the benefits of remote control.
When the wireless telephone system supports remote control for a plurality of household appliances, the user cannot determine the control state of any appliance with either the base unit or handset, even such simple information as which appliances or on and which are off, because the base unit and handset receive no data feedback from the household appliances. Hence, the user cannot determine the control status of individual household appliances and perform desired control operations for each appliance individually, but can only perform limited control operations, such as switching the power off on all appliances at the same time.
In order to use infrared remote control communications to control the electric devices, conventional wireless telephone systems use infrared communications to communicate with the electric devices unidirectionally. Since infrared signals from a remote controller have an extremely short traveling distance and do not have a strong ability to pass through or around objects, an infrared signal used within a room or other space enclosed by walls are not likely to be transmitted outside the enclosed space. When a base unit employing infrared communications is used as the primary remote controller, for example, the base unit can only control appliances within the same room. Hence, if the structure of a wireless telephone system is used to control household appliances in each room that a base unit or handset is present, then an infrared signal transmitter must be provided in the handsets as well as the base unit. Further, the data transmission capacity in infrared communications is limited.